The Driniumor River lies approximately 20 mi (32 km) east of Aitape on the north coast of what was part of the Territory of New Guinea at the time of the battle.

[2] On 22 April 1944, Allied forces landed at several key points around Hollandia and seized Aitape as part of Operations Reckless and Persecution.

After the seizure of Aitape, the U.S. 163rd Regimental Combat Team (163rd RCT) consolidated their positions until early May when they were relieved by the 32nd Infantry Division under Major general William H. Gill.

A defensive perimeter was established around the airfields in the area, eventually extending 30 miles (48 km) east of Aitape, including several outposts along the Dandriwad River.

[9][10] In the lead up to the battle, the Japanese established their westward supply lines, constructing a 60 km (37 mi) road from Wewak and installed a series of coastal defenses to protect water transportation operations.

[12] As early as late May, General Walter Krueger ordered reinforcements into the area in response to a range of intelligence about the Japanese buildup.

[17] Further intelligence, including information gained from fighting patrols, led to American troops being placed on alert in expectation of a Japanese assault on several occasions in late June and early July.

[3] The initial attack was poorly coordinated, being hampered by the terrain, which resulted in the 78th launching their assault 20 minutes before the 80th who were followed by the main elements of the 237th around 02:00 hours on 11 July.

A secondary attack began at around 05:00 hours when follow on elements of the Japanese 237th Infantry Regiment, along with supporting medical, staff and artillery personnel crossed the Driniumor.

This secondary movement continued until around dawn when elements of the two main Japanese assault regiments—the 78th and 80th—began reorganising on high ground about 800 yards (730 m) northwest of the U.S. line.

This inflicted heavy casualties on the Japanese and destroyed large amounts of equipment including machine guns and indirect fire support weapons.

[30] This effort resulted in heavy clashes with elements of the U.S. 112th Cavalry and 127th Infantry Regiments on the southern flank of the Allied line,[31] but failed to permanently secure the village for the Japanese who captured it at least twice, before being forced to withdraw.

[3] After the first effort against Afua, the remainder of July saw heavy fighting west of the river as platoon/troop, company/squadron and battalion-sized units clashed in the jungle along the coast and around the Torricelli Mountains.

The Japanese forces on their right flank near the coast then switched to the defensive, offering strong resistance before attempting to resupply and reorganize around Yakamul and Maljip.

During this time, U.S. troops patrolled towards Marubian, Charov and Jalup, but were unable to reestablish contact until reaching strong positions on the Dandriwad River.

Allied PT boats and destroyers also interdicted Japanese barge supply convoys between Aitape and Wewak and fired upon troop concentrations along coastal avenues of advance.

[16] The four-week Battle of Driniumor River was one of the costliest of the campaigns in Papua and New Guinea, second only to the bloody head-on Allied assaults of the Japanese strongholds at Gona, Buna and Sanananda from November 1942 – January 1943.